Photoflash lamp



1963 E. w. DESAULNIERS 3,114,250

PHOTOFLASH LAMP Filed Dec. 18, 1962 E UGENE W. DESAULNIERS INVENTOR.

ATTOR EY United States Patent 3,114,250 PHQTOFLASH LAMP Eugene Y]. Desaulniers, Williamsport, Pa, assignor to Sylvania Electric Products Inc, a corporation of Belaware Filed Dec. is, 1962, Ser. No. 245,598 6 Claims. (31. 67-31) This invention relates to the manufacture of photoflash lamps and more particularly to those photo-flash lamps in which shredded zirconium foil is employed as the combustible light-producing material.

In recent years shredded zirconium foil has been used more and more extensively and has gradually replaced shredded aluminum foil as the combustible light-producing material in many photof ash lamps. Although, for many years, those skilled in the art considered zirconium and aluminum as substantially equivalent to one another insofar as their use as the combustible light-producing material in photofiash lamps is concerned, it has been discovered more recently that such is not the case. As a matter of fact, it has been discovered that these two materials differ significantly from one another in a number of different performance characteristics. Some of these differences in performance characteristics provide direct advantages attainable when zirconium is used instead of aluminum as the combustible light-producing material. On the other hand, there are other characteristics, which distinguish zirconium from aluminum, which po se certain problems in connection with the use of zirconium which were not encountered heretofore when aluminum was used as the combustible. One of these problems is ignition control, particularly insofar as it relates to the time interval between closing of the ignition circuit and the attainment of peak light intensity by the combustible.

Because of the relatively low heat-energy ignition characteristic of zirconium and its exceedingly fast ignition, the peak intensity of the light produced occurs within a considerably shorter interval of time than it does when aluminum is employed as the combustible. This shorter time to peak intensity is particularly noticeable when smaller and smaller lamp envelopes filled with a combusdon-supporting gas at higher and higher pressures are employed. More particularly, this shorter time to peak intensity is paiticu arly acute when lamp envelopes smaller than about 10 cc. internal volume and pressures above atmospheric are employed.

Control of the time to peak intensity is essential in order to permit use of the lamp effectively for class M as well as class F synchronization. Over the years, when aluminum was employed as the combustible, adequate controls were developed. These controls included, for example, regulation of the primer bead size and choice of foil shred size, i.e., cross-sectional area. However, zirconium is far less controllable with changes in primer head size due to its exceedingly fast ignition, and practical limitations from a manufacturing viewpoint, particularly in high speed operations, preclude effectuation of this control by shred size regulation.

Some control can be attained by using extremely small primer beads and/or by the incorporation of inert additives in the primer composition. However, both of these controls have substantial disadvantages Extremely small primer beads are impractical from a manufacturing viewpoint because size control thereof in high speed operations is a practical impossibility. Flashing reliability can be adversely affected when inert substances are incorporated into the primer because these substances tend to lower the available heat norm-ally supplied by the ignition filament.

In view of the foregoing, a principal object of this invention is to provide an efiicient, reliable ignition timing control for zirconium foil fiashlarnps which can be readily 3,114,256 Patented Dec. 17, 1963 2 employed in high speed lamp manufacturing operations. In accordance with the principles of my invention, this and other objects and advantages are attained b providing the zirconium foil with an ultnathin film of zirconium oxide.

Zirconium belongs to the class of metals which form oxide when made anodic in most aqeous solutions. Thin oxide films can be controllably grown utilizing this process. A blue-gray oxide film on both sides of the zirconium foil sufiiciently retards the fast ignition characteristic of the foil to permit utilization of a standard igniter. The film should be at least about 400 Angstroms thick to effect the desired retardation. The film should not be more than about 1560 Angst-rorns thick because of an adverse effect on total light output.

In some applications of the use of zirconium foil as the combustible in the manufacture of photoflash lamps it has been found desirable to use annealed foil and in other applications annealing does not appear to be preferable. l have found that my invention may be practiced with beneficial results with both annealed and unannealed zirconium foil.

in the accompanying drawing one type of photofiash lamp with which my invention may be practiced is illustrated in the single figure. The lamp comprises an hermetically sealed, light-t-ransnntting glass bulb 2, having an internal volume of about 7 cc., and being provided with a filling of combustion-supporting gas such as oxygen at a pressure of about cms, and shredded zirconium foil 4. The bulb 2 is provided with a base 6 aifixed to the neck thereof. A filament 8, the ends of which are attached to lead-in wire-s 1t and 12, is disposed within the bulb 2. The inner ends of the lead-in wires 19 and 1.2 are provided with a body of ignition paste or primer 1d. The lead-in wires 1t and 12. are connected to conventional Ibase contacts in the usual manner.

In the tabular dataset forth below, all of the lamps tested were of the type described immediately above and in each instance the zirconium foil was about .06095" X 002 in cross section and about 4 long. About 42.5 rugs. of this foil was used as the fill for each lamp.

The following test data indicates the beneficial effects which can be obtained by providing the zirconium foil, annealed or unannealed, with an ultra thin film of zirconium oxide. 'In each instmce this film was about 900 Angstrorns thick and was formed by anodizing 4 x 4" sheets of zirconium foil in a- 14% by Weight solution of HNO at a current density of 2 mix/cm? until the supply voltage reached 10% volts DC. (approidmately 18 min). The anodized sheets were then shredded in the usual manher to provide anodized filamentary foil.

In the foregoing tests, no significant differences in total light output were noted, but yet several significant advantageous effects were obtained, viz., the time to peak was lengthened, the pea: height was shortened and the one-half peak duration was lengthened. Collectively, these three elfects are noteworthy because the resultant light output curve is flatter, extends over a longer period of time and a more uniform quantity of light over a longer period of time is obtained during the onehalf .peak interval. This broader one-half peak duration characteristic makes possible a broader application of high speed focal plane shutter usage than generally recommended heretofore.

What I claim is:

1. A photofiash lamp comprising: a sealed light-transmitting envelope; :1 combustion-supporting gas filling in said envelope; a quantity of anodized filamentary zirconium disposed in said envelope; and ignition means disposed in said envelope in operative relationship with respect to said anodized filamentary zirconium.

2. A PllOtOflBSl'l lamp comprising: a sealed light-trans nri-tting envelope; at combustion-supporting gas filling in said envelo' e. quantity of filamentary zirconium disposed in said envelope; 2. film. of reonium oxide on said filamentary zircon" iin, said film b big between about 460 to about 1500 Angstrom units thick; and ignition means disposed in said envelope in operative relationship with respect to said filamentary zirconium.

3. A photoflash lamp comprising: a sealed light-transmit-ting envelope having an internal volume of less than about 7 0a.; a combusdon-supporting gas filling in said envelope; a quantity of anodized filamentary zirconium disposed in said envelope; and ignition means disposed in said en 'elope in operative relationship with respect to said anodized filamentary zirconium.

4. A photoilash lamp comprising: a sealed light-transmitting envelope; a combustion-suppopting gas filling at a pressure above atmospheric in said envelope; :1 quantity said envelope; n quar ity of anodized unonnealed filamentary zirconium disposed in said envelope; and ignition means disposed in said envelope in operative relationship with respect to said anodized unannealed filamentary zir- COfii'llIll.

References Qiied in the file of this patent UNITED STATES PATENTS 2,011,771 Miller Aug. 20, 1935 2,177,108 Highriter Oct. 24, 1939 2,215,477 Ripkin Sept. 24, 194%) 2,254,849 Kreider Sept. 2, 1941 

5. A PHOTOFLASH LAMP COMPRISING: A SEALED LIGHT-TRANSMITTING ENVELOPE; COMBUSTION-SUPPORTING GAS FILLING IN SAID ENVELOPE; A QUANTITY OF ANODIZED ANNEALED FILAMENTARY ZIRCONIUM DISPOSED IN SAID ENVELOPE; AND IGNITION MEANS DISPOSED IN SAID ENVELOPE IN OPERATIVE RELATIONSHIP WITH RESPECT TO SAID ANODIZED ANNEALED FILAMENTARY ZIRCONIUM. 